We will continue current investigations of cellular energy metabolism during fetal and newborn development. Fatty acid metabolism in developing lung and brain will be characterized and we will study hormonal and nutritional influences on enzymes of fatty acid synthesis and oxidation in these tissues. We will also investigate substrate preferences and oxidative metabolism by isolated lung and brain mitochondria as influenced by hormones and nutritional state. We are particularly interested in cortisol, thyroxin and insulin effects on lung and brain fatty acid synthesis. Developing rats will be nutritionally deprived and hormonal influences will be determined following administration of hormones to fetuses and newborns. We will further characterize the palmitylcarnitine transferase system during development by investigating palmitylcarnitine transferase activity of mitochondrial membrane fractions during early development. A major goal will be to correlate binding of insulin and catecholamines to developing cells with known metabolic effects of the hormones. This should help define critical periods during development when hormones can exert effects on cell metabolism. This includes investigations of influences on cell growth and metabolism using tissue culture of embryonic and newborn myocardial and skeletal muscle. Binding of hormones (insulin and catecholamines) to cultured cells will be related to metabolic effects including fatty acid and glucose oxidation, lactate and pyruvate production and glycogen metabolism by cultured cells. Cultured skeletal muscle will be utilized to investigate hormonal and nutritional influences on glugoneogenesis. The release of alanine by muscle cells exposed to different challenges will be determined. These studies will hopefully provide a better understanding of the control of energy homeostasis and hormonal regulation of cell growth and metabolism during development.